"Why would they leave?" said Holtz-Eakin. "What they are getting from their employer is way better than what they could get with the credit."

Obama seized on that comment, saying, "This is the point I've been making since Sen. McCain unveiled his plan. It took until the last seven days of this election for his campaign to finally admit the truth. But, better late than never.

The truth is, John McCain's health care plan is radical, it's unaffordable, it's not the change we need right now."

McCain and Obama take very different paths to what they say is the same endpoint -- reforming health care.

As part of McCain's plan, employees would lose the tax exemption for company-sponsored health insurance. Instead, taxpayers would get a refundable tax credit of $2,500 for single filers, or $5,000 for families, to cover the costs of insurance bought on the job or on their own in the individual market.

Doing this, McCain says, would level the playing field between those who get insurance on the job, where benefits aren't taxed, and those who buy it their own, where it is subject to tax. The tax credit would let more of the uninsured afford coverage.

Don't Miss

Obama, on the other hand, is promising to push employers to cover more Americans as part of his health care proposal. He would require larger companies provide insurance to employees or contribute toward the cost of a national plan, while giving small businesses a tax credit to entice them to offer coverage to their workers.

Meanwhile, McCain and Obama on Tuesday pounced on each other's tax proposals as they campaigned 90 miles apart in Pennsylvania.

"John McCain's ridden shotgun as George Bush has driven our economy toward a cliff, and now he wants to take the wheel and step on the gas," Obama said at a rainy rally in Chester, Pennsylvania.

"When it comes to the issue of taxes -- saying that John McCain is running for a third Bush term isn't being fair to George Bush," he said.

In Pennsylvania, Obama leads by 10 percentage points, 52 percent to 42 percent, but McCain's campaign has said it is buoyed by internal numbers not showing up in public polling. Watch the latest on battleground polls »

The state has 21 electoral votes up for grabs. Pennsylvanians have voted for the Democratic nominee in each of the last four presidential elections.

As McCain tries to gain ground in the final week of campaigning, he's been warning voters that an Obama win would mean an unchecked Democratic Congress.

"My opponent is working out the details with Speaker [Nancy] Pelosi and Sen. [Harry] Reid of their plans to raise your taxes, increase spending and concede defeat in Iraq," McCain said at his rally in Hershey, Pennsylvania.

"It's interesting how their definition of rich has a way of creeping down," McCain said, pointing to an interview Monday in which Democratic vice presidential candidate Sen. Joe Biden referred to the middle class as "people making under $150,000 a year" and an Obama ad that says $200,000 is the threshold for a tax cut.

The Obama campaign said McCain's attacks "are getting more desperate by the hour."

"As Obama and Biden have always said, under their plan no family making less than $250,000 will see their taxes increase 1 cent. And if your family makes less than $200,000 -- as 95 percent of workers and their families do -- you'll get a tax cut," said Obama-Biden campaign spokesman Tommy Vietor.

Under Obama's plan, those who make between $200,000 and $250,000 would not see their taxes change. Those making less than that would get at least a partial credit, while those making more would see their taxes go up.

Following their Pennsylvania events, both candidates were headed south, with Obama going to Virginia and McCain to North Carolina.Track candidate visits

In Virginia, Obama leads McCain by 7 percentage points, 51 percent to 44 percent, according to CNN's average of state polls. State-by-state polling

In North Carolina, Obama is up by 4 points, 51 percent to 47 percent, according to a CNN/Time/Opinion Research Corp. poll.

That poll was conducted October 19-21 and has a margin of error of plus or minus 4 percentage points.

Nationally, Obama leads McCain by 8 percentage points, 51 percent to 43 percent, according to CNN's average of national polls.